The news comes after The Daily Telegraph revealed that 20 Government ministers - including seven members of the Cabinet - have campaigned or are campaigning against closures in their local constituencies. The plans to close 2,500 branches are said to be necessary to preserve the Post Office network's £150 million-a-year subsidy and cut its estimated losses of £4 million a week.

So far, half of the planned closures have been announced. However, in a letter to sub-post masters, Post Office managers warn that the programme will be frozen during the local elections. They are concerned that the closures could become a "local political issue" and so have agreed to suspend the programme during the campaign.

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The letter says: "London Mayoral elections and Local Authority elections in England and Wales will be held in May 2008. As you will be aware, the closure of any post office can be highly sensitive and can potentially become a local political issue.

"For that reason, we have been asked by Government to introduce a freeze on some elements of the Network Change Programme during the run-up to these elections."

The ban applies from April 7 to May 2. One sub-postmaster said: "This has incensed me. They feel it is very sensitive. They have suspended the closure programme because they don't want to lose votes in the election." Charles Hendry, the Conservatives' post office spokesman, said: "The Government is being breathtakingly cynical with this approach.''

However, a spokesman for the Department for Business defended the move. He said: "Due to the application of normal purdah procedures which apply during election periods, no public consultations will take place and no network change announcements will be made between April 7 and May 2."

Closure plans are important issues at a local level, prompting many senior Cabinet ministers, such as Jack Straw, the Justice Secretary, to campaign to keep post offices open - despite approving plans to close thousands.